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Chiral salen ligands designed to form polymetallic complexes

Lookup NU author(s): Thierry Achard, Emeritus Professor Bill Clegg, Dr Ross Harrington, Professor Michael North

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Abstract

Chiral salen ligands capable of forming polymetallic complexes have been designed. The ligands possess substituents in the 4,4'-positions, but have no substituent in the 3,3'-positions to allow a second metal ion access to the salen oxygen atoms. Ligands in which a polyether chain links the 4,4'-positions were prepared and complexed to copper. In addition, acyclic ligands with potential metal coordinating substituents in the 4,4'-positions were prepared and complexed to copper and cobalt. The crystal structure of one of the cobalt complexes shows it to be a trimetallic complex in which a Co(II)(OAc)(2) group coordinates to the salen oxygen atoms of two Co(Ill)(salen)(OAc) units. In contrast, the crystal structure of a Co(salen) complex with tert-butyl groups attached to the 3,3'-positions is found to be mononuclear. All of the complexes were tested as asymmetric phase transfer catalysts for the asymmetric alkylation of an alanine methyl ester, forming (R)-alpha-methyl phenylalanine methyl ester with up to 85% ee. (C) 2011 Elsevier Ltd. All rights reserved.


Publication metadata

Author(s): Achard TRJ, Clegg W, Harrington RW, North M

Publication type: Article

Publication status: Published

Journal: Tetrahedron

Year: 2012

Volume: 68

Issue: 1

Pages: 133-144

Print publication date: 31/10/2011

ISSN (print): 0040-4020

ISSN (electronic): 1464-5416

Publisher: Pergamon

URL: http://dx.doi.org/10.1016/j.tet.2011.10.084

DOI: 10.1016/j.tet.2011.10.084


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